1. The Field of the Invention
The field of the invention relates to an improved purge valve assembly useful in large scale power boilers which burn No. 6 bunker oil when such boilers are to be shut down.
2. Description of the Prior Art
Large scale power boilers which operate by burning No. 6 (Bunker) oil require hot purging of the fuel upon shut down. Failure to do so will cause the fuel to become viscous or carbonized as it cools thereby causing the burner and adjacent feeds to become clogged U.S. Pat. No. 4,823,843 (Apr. 25, 1989 to Golembiski) discloses a valve apparatus based upon a lost motion coupler to actuate steam and fuel valves to give either steam and fuel concurrently to facilitate atomization and burn, recirculate fuel or provide a steam purge. These are the basic requirements of boiler systems of the type. U.S. Pat. No. 4,146,056 (Mar. 27, 1979 to Buchanan) discloses a purge valve with linear actuation. Combustion Engineering, Inc. has a purge valve network which performs the operations essentially in the manual mode.
Each of the foregoing has limitations caused by the harsh environment of high pressure steam and liquified No. 6 oil. For example, failure in the field of parts from thermal stresses, the passage through them of steam at 550 degrees Fahrenheit at 300 psi and the like is a common occurrence. Under the circumstances, maintenance can be difficult and complex.